1. Field of the Invention
The present invention relates to a reinforced pallet.
2. Background Art
Pallets are subject to many types of loads and forces. Many of these loads and forces are illustrated by pallet racking scenarios and line load scenarios. The line load is the weight of a unit load concentrated along a narrow area across the full length or width of the pallet. The rack load is the load carrying capacity and deflection of a pallet which is supported by a rack frame near the ends of the pallet stringers.
Today, the use of plastic pallets is becoming more common. While reinforced plastic pallets presently exist, most do not provide sufficient reinforcement for racking loads and line loads. For example, a non-continuous, multiple piece cross-reinforcement may do little to support racking loads.
Some reinforced pallets today may attempt to handle various load types, such as line loads and racking loads, but are ultimately not size efficient or cost efficient. In other words, these pallets may not provide the end user with the desired strength and load bearing properties for the desired pallet package height. For example, in certain reinforced plastic pallets, the deck in which the reinforcement is located may be significantly larger than its unreinforced counterparts. In such a reinforced deck, the reinforcements may overlap in different planes, resulting in a larger deck height, and an overall larger pallet height.
Moreover, many reinforced pallets have reinforcement which is exposed. This is a particularly undesirable feature in the case where the reinforcement is made from fiberglass or other fiber material, which may eventually delaminate and cause the pallet to have less durability and a shorter pallet life.
Pallets formed of molded plastic material have distinct advantages over those made of wood or metal. While wood pallets have sufficient stiffness, they are heavy; are subject to warpage, splintering and splitting; are nonuniform in strength; and gain significant weight when wet. Metallic pallets typically are expensive and, in the case of steel, heavy and subject to corrosion. Plastic pallets are stronger, lighter and more durable than wooden pallets. Traditionally, fire retardance as it relates to plastic pallets has not been recognized as an issue. However, recently, plastic pallets have been the subject of standards promulgated by the National Fire Protection Association (NFPA), Underwriters Laboratories Inc. (UL), Factory Mutual Research Company (FMRC), and National Association of Fire Marshals.
Some standards allow for plastic pallets to be used the same as wood pallets when experimental data show equivalency in the burning and suppression characteristics between the plastic and wood pallets. Unfortunately, some material presently used to help promote fire retardance in plastic pallets, such as an engineered resin blend of high-impact polystyrene and polyphenylene oxide, is very expensive and thus not cost efficient to mold an entire pallet from this material. Such material may also not be as injection-molding friendly as other polymeric materials.
Accordingly, a reinforced plastic pallet is desired which is capable of handling the various loads to which a pallet may be subjected, including both line loads and racking loads. The pallets should have a package height comparable to an unreinforced pallet. The pallet and reinforcement should also be durable, provide for improved pallet life, and should be cost efficient. Moreover, a pallet is desired which is accepted by the fire community as having burn and suppression properties substantially similar or better than wood, is relatively inexpensive, lightweight, and easy to manufacture.